Mobile communication devices being electrical in nature have various voltages and currents, which are present in the device in varying amounts at different points and/or in different portions of the device. Associated with the various voltages and currents are corresponding electrical and magnetic fields, which in turn can induce various voltages and currents in other nearby devices, which interact with the fields. Some of the induced voltages and/or currents may be unwanted or detrimental to the operation of one or both of the devices.
One such potential interaction can occur between a hearing aid and a cellular telephone, where currents associated with the transmission of wireless communication signals in the radio frequency range can produce nearby electrical and magnetic field, which interact with the hearing aid, and more specifically the components and or the interconnects between the components of the hearing aid, such an interaction can produce unwanted noise and interference resulting in audio distortion at the output of the hearing aid at levels which are detectable by the user and which interferes with reproduction of the desired audio sounds for which the device is intended to enhance and correspondingly convey to the user.
The unwanted audio distortion can be addressed in at least a couple of different ways. First, the hearing aid can be hardened so as to have greater immunity to nearby electrical or magnetic fields, or second, the associated electrical device, which are producing the potentially offending electrical and/or magnetic fields, can be designed to produce and/or emit lower levels of electrical or magnetic energy in the areas that are more proximate the likely location of hearing aid during the joint usage of the same. With respect to a cellular telephone, the affected area is traditionally proximate the location of the speaker and/or the porting of the speaker, which is intended to produce the sounds to be detected by the user.
In an attempt to address the issue, the United States Federal Communication Commission has passed guidelines, which require the identification of a hearing aid compatibility rating for all cell phones, and has further required that manufacturers of cell phones have a certain number and/or percentage of devices that meet or exceed a ratings level that is deemed to be passing at each of several different designated points in time. The different designated points in time serve to allow for the phasing in of requirements relative to a corresponding portion of a manufacturer's portfolio of offered products. Presently, cell phones are being tested for RF emissions according to the ANSI C63.19 standard. The standard provides for an “M” rating for use with hearing aids set in microphone mode, where passing ratings of M3 and M4, respectively correspond to a rating of good and excellent. The standard additionally provides for a “T” rating for use with hearing aids set in telecoil mode, where passing ratings of T3 and T4, respectively similarly correspond to a rating of good and excellent.
Currently, the specific test involves a 3×3 square planar grid (measuring 5×5 centimeters) that is centered about the audio ear piece speaker of the cellular telephone and is suspended one centimeter above the surface of the audio porting. Within the 3×3 grid, the electric and magnetic fields are separately measured for each of the nine regions at each of a couple of different frequencies, where the field strength cannot exceed a predefined level in at least six of the nine regions. In other words, up to three of the regions can be excluded (i.e. they can exceed the predefined level), so long as they are continuous, and so long as the regions to be excluded do not include the center region. The possibility that up to three regions can be excluded envisions the possibility that a user can shift the position of the cellular phone relative to the hearing aid a certain amount so as to avoid the three regions, which might exceed the predefined acceptable field strength levels, and still achieve an acceptable level of interactive performance between the two devices.
However, in at least some instances, the currents and voltages, which are producing at least a portion of the offending electrical and magnetic energy, are related to the intentional production and radiation of radio frequency energy, which is being emitted for the purpose of communicating with a remotely located receiver, transmitter and/or transceiver. Because the transmission and reception of radio frequency signals is central to the functioning of a cellular telephone, it is not always a simple matter to eliminate all of the sources of the offending fields, as some of the fields in the frequencies of interest are necessary for supporting the radio frequency communications with the cellular infrastructure.
As a result, it would be beneficial to develop a system or manner in which the electrical and/or magnetic fields proximate the ear piece speaker or other audio signal output device of a radio frequency communication device can be reduced and/or redirected so as to enhance the quality of interaction with other nearby electrical devices, such as a hearing aid without substantially sacrificing radio frequency communication capabilities.